[Iftah] has been exploring the sounds beyond what we can hear, recording ultrasound and pitching it down. He made a short video on the practice, and it’s like a whole new world of sounds exists just outside of our hearing.
For instance, a dropped toothpick sounds like you’ve just dropped a piece of lumber, a broken lightbulb sounds like a shattered window, and a blackbird sounds like a blue whale. Besides simply sounding super, [Iftah] speculates that there’s some regularity here: that as you slow down the sound it sounds like it came from sources that are physically bigger. He follows this up in a second video, but if you just think about the basic physics, it makes sense.
If you’re interested in recording your own ultrasound, there are a bunch of options on the market. With modern audio processors running up to 192 kHz or even 384 kHz out of the box, all that’s missing is the high-frequency-capable microphone. Those aren’t unobtainable anymore either with many MEMS mics performing well above their rated frequency response specs. Recording ultrasound sounds like a fun and not-too-expensive project to us!
Of course, most of the ultrasound recording we’ve seen has been about the bats. Check out the Pipistrelle or this pair of DIY bat detectors for some good background. But after watching [Iftah]’s video, we’re no longer convinced that the cute little insectivores are the coolest thing going on in the ultrasound.
Interesting how everything sounds exactly like it would if the objects were much larger.
Interesting, but not surprising. Even in daily life you might notice that large humans tend to have deeper voices than small humans. More volume = space for larger resonant waves to build up.
Writing that bats are insectivores is like writing that all presidents eat only burgers.
Many bats species eat only fruits. Some other even feed on mammal blood. And yes, some eat insects.
As a sound designer, I’ve also done a lot of ultrasonic recordings, some unintentionally. One summer evening, I was trying to capture the sound of frogs and crickets. I had my recording levels set appropriately for those sounds. However, I was frequently seeing the level meters jump to full scale and the clipping indicators occasionally flashed. I thought I might have a faulty connection to my mics as I certainly wasn’t hearing anything that would cause that. When I got my recordings onto my edit machine in the studio, the meters in my DAW did the same thing and I could see the waveform had many very loud segments even though they sounded the same as the quieter parts. When I switched to a spectrogram view, I saw a lot of loud activity captured around 40 kHz and higher. It was bats. When slowed down a few octaves, it was very cool to hear these otherworldly bird-like sounds. Additionally, I heard the same echolocation phenomenon he describes where the individual chirps got closer together as the bat zeroed in on its target. It was similar to hearing a ball bearing bouncing on a hard surface as the delay between bounces converges to zero.